The present invention relates to a beveling machine for machining the heads of large- and medium-diameter pipes, or more generally pipes of any diameter, such as pipes of oil pipelines, gas pipelines, and piping in general, particularly submarine piping arranged vertically or subvertically as well as vertical pipes constituting the supporting and foundation piling of offshore rigs.
More particularly, the invention relates to beveling machines that are adapted to form welding bevels or chamfers on the ends of such pipes and comprise an expander means and a machining head, which are combined and cooperate so that the expander means engages, by means of the radial expansion of its anchoring elements, the internal surface of the pipe being machined in order to center and retain the entire machine, and so that the machining head, which is meant to remain outside the pipe, supports and moves one or more tools that rotate around the pipe, performing the required chip-forming machining. For this purpose, the machining head is provided with a rotating disk, which is typically actuated by one or more hydraulic motors and is provided with a plurality of tool holders that can move radially and/or axially.
Although the assembly constituted by the machining head and the corresponding tool holders is structured so as to be very rigid, the machining standard of these known types of beveling machine is rather modest and is often unacceptable in modem fully automatic welding processes, in which the exactness of the profile of the welding bevel or chamfer is an absolutely critical and indispensable parameter in terms of the corresponding correct execution of said welding process. Usually, the imperfection of the machining performed by known types of beveling machine substantially depends on vibrations of the tool holders, which are transmitted to the entire machine and increase as the thickness and the mechanical characteristics of the material of the pipes being machined increase; both of these parameters have increased considerably in recent times, especially in the field of submarine piping, where the use of said known types of beveling machine is now fully inadequate. Furthermore, these known beveling machines are shaped so that they can work usefully essentially on pipes that are arranged horizontally, but some of the submarine piping is also produced, as is known, by welding together vertical or subvertical piping sections (with maximum inclinations of approximately 20xc2x0), which are then sunk without altering their vertical or subvertical arrangement. These production methods, too, cause the use of such known beveling machines to be inadequate in the laying of submarine piping and more generally in the laying of vertical pipes, for example for submarine piling and foundations.
The aim of the present invention, starting from the notion of these drawbacks and limitations of known beveling machines, is to eliminate them. Within this aim, an object of the present invention is to provide a beveling machine that is vibration-free and therefore capable of performing chip-forming machining operations that are extremely accurate and capable of producing bevels having a profile that is substantially equivalent to the profile that can be obtained with actual machine tools having a high quality standard.
Another object of the present invention is to provide a beveling machine that is adapted to machine the ends of pipes arranged vertically or subvertically as specified and is therefore especially adapted for machining the ends of pipes of submarine pipelines or of pipes of submarine piling and the like. In particular, a further object of the present invention is to provide a beveling machine that is also capable of performing selectively or simultaneously machining operations on mutually opposite ends of a pipeline divided into two vertical (or subvertical) segments between which the beveling machine proper is interposed.
This aim and these and other objects that will become better apparent hereinafter from the following detailed description are achieved with a beveling machine having the specific characteristics defined in the appended claims.
Substantially, the invention is based on the concept of providing a twin-head beveling machine that comprises two mutually opposite pressers and machining heads of the rotating-disk type, the pressers being rigidly connected to each other by a central fixed shaft, the machining heads being mounted so that they can rotate and move axially individually on the central fixed shaft and being subjected to the action of hydraulic or pneumatic motor means and of axial movement means, activated by a respective hydraulic or pneumatic actuator, which produce the axial working advancement of the respective head.
Furthermore, and substantially with the aim of eliminating vibrations so as to make the machine suitable to perform machining operations having the same machining standard as machine tools, the rotating disks of the machining heads have oscillating tool holders, each of which is provided with a respective sliding block subjected to the action of a retention means that is typically constituted by a clamping element and is adapted to limit or block completely the oscillation of the respective tool holder.